add useSessionStorage hook

[createdbymahmood]

Hi. This PR is related to #85:

• adds useEventCallback hook
• adds useSessionStorage hook
• wraps useLocalStorage setValue function using useEventCallback

I also need some help to add docs for useSessionStorage.

[juliencrn]

Again, thanks @createdbymahmood. 👏
This hook was wanted! (#85)

I've just added a demo and content files.
For the next time you want to create a new hook, please consider using the npm run plop CLI generator.
This cmd will create all the boilerplate for you ;)

PS: great addition, the useEventCallback 👍